The turbine engine of an airplane runs at ground idle speed while the aircraft is taxiing into an airport station or taxiing out to the runway in preparation for take-off. Ground idle is a throttle position which maintains a moderately low thrust at which the engine may be operated suitable for specific ground conditions. Taxiing with the engine operating at ground idle thrust, however, should be kept to a minimum since the engine thrust is sufficiently high to cause the brakes to wear relatively fast. In addition, fuel consumption while taxiing at ground idle is also relatively high. Furthermore, the ground idle thrust may cause the aircraft to be difficult to control on slippery runways coated with ice or snow.
A thrust reverser mechanism may be incorporated in the engine to help reduce the thrust of an airplane turbine engine to solve the above mentioned problem. However, a thrust reverser mechanism would have to be generally controlled by a separate set of control throttles which would mean more equipment in the pilot's already crowded cockpit. In addition to the fact that the pilot would be forced to become familiar with still another set of complicated controls, when the thrust reverser mechanism is utilized at the low ground idle speed, there may be a tendency for exhaust gases to reenter the air inlet which could result in compressor surge and an excessive exhaust gas temperature.
Alternatively, the existing throttle could be modified to include another position corresponding to a lower thrust. This arrangement would entail further complicating the throttle. More particularly, safety precautions would require another detent added to the throttle to prevent the pilot from moving into the lower thrust position too soon, and thus losing power unnecessarily.
Accordingly, there is a need for a safe and efficient apparatus for reducing the thrust of the turbine engine of an airplane while the airplane is taxiing.
In view of the above it is an object of the subject invention to provide a sub-idle speed control apparatus for reducing the thrust of a turbine engine of an airplane while the airplane is taxiing to reduce brake wear and mimimize fuel consumption.
It is another object of the subject invention to provide a sub-idle speed control apparatus for reducing the thrust of a turbine engine of an airplane that is separate and distinct from the throttle.
It is a further object of the subject invention to provide a sub-idle speed control apparatus for reducing the thrust of a turbine engine of an airplane that enables the pilot to select a lower engine speed while at ground idle.
It is an additional object of the subject invention to provide a sub-idle speed control apparatus for reducing the thrust of a turbine engine of an airplane that can only be activated while the airplane is on the ground.